Try updating your mod. If you still have v7's, you're out of date. Link to the Softmod Any Wii guide is in my signature.
Once you do that, if you try the latest CFG, you can tell it to run the game from IOS = Auto and it should auto-detect.
There is no cIOS based off of 21 that I know of, so it may be running off of something else? Other Namco Museum games based on what I found looks like runs on 33, but there is no cIOS based off of that either.
So, for now, try updating the mod using our guide, that might help by itself. If not, try CFG's Auto IOS feature.